!(function(doc, win) {
	    var docEle = doc.documentElement,
	        evt = "onorientationchange" in window ? "orientationchange" : "resize",
	        fn = function() {
	            var width = docEle.clientWidth;
	            width && (docEle.style.fontSize = 20 * (width / 320) + "px");
	            if(width >= 640) {
	            	docEle.style.fontSize = 30.1875 + "px";
	            }
	        };
	     
	    win.addEventListener(evt, fn, false);
	    doc.addEventListener("DOMContentLoaded", fn, false);
	 
	}(document, window));